The invention relates to a cassette with magnetic tape on two coplanar reels and comprising: a housing having a main wall formed with two openings for reel spindles of a drive apparatus, two coplanar rotatable reel hubs which are coaxial with the openings and having central means for cooperation with the reel spindles, a slide cover which is slidable on the housing between an open position, in which the openings are not covered, and a closed position, in which the openings are covered, and blocking members movable between a blocking position and a non-blocking operating position which cooperate with the reel hubs to inhibit their rotation in the blocking position and which do not obstruct the reel hubs to allow their rotation in the operating position.
A cassette of this type, referred to as an RDAT cassette, is known, for example from European Patent Application 0,210,854 A2 which corresponds to U.S. Pat. No. 4,714,213 (herewith incorporated by reference). The known cassette is of the non-reversible type, so that only one of the two main walls has openings for reel spindles. A slide cover is slidable over this main wall, from the front to the rear of the cassette. The slide cover has openings corresponding to openings in the adjacent main wall. In the closed position the openings in the main wall are covered and the corresponding openings in the slide cover imperforate parts of the main wall. In the open position the openings in the main wall and the slide cover are coaxial to provide free access to the reel hubs for the reel spindles. A hinged shutter is situated at the front of the cassette to cover a part of the magnetic tape which extends along the cassette front in a closed position of this shutter. To use the cassette on an apparatus both the slide cover and the shutter are moved from their closed to their open positions. In the interior of the cassette housing a blocking member has been provided for cooperation with the hinged shutter, which member takes the form of a plate having two projections, which plate is slidable from the front to the rear of the cassette. Inside the housing the plate is movable over the imperforate main wall. At an end facing the imperforate main wall each of the two reel hubs has been provided with teeth at its outer circumference. When the shutter is closed the projections of the blocking member engage the teeth of the reel hubs to inhibit rotation of the reel hubs. When the shutter is opened the blocking member is pulled towards the front of the cassette against spring force by cooperation with the shutter, so that the projections are disengaged from the teeth to allow rotation of the reel hubs.
Generally speaking, it is important to block the reel hubs of a cassette as long as the cassette is not in a drive apparatus. Indeed, if the reel hubs are not blocked, movements of the cassette, for example when it is handled or as a result of vibrations in a storage rack in a car, are likely to give rise to a rotation of the reel hubs with consequent looping of the magnetic tape. This may result in damage to the magnetic tape and possibly in malfunctioning of the cassette in a drive apparatus. For the well-known Compact Cassettes, in which as is known the openings in the two main walls are not closed, this problem has been solved by providing a special storage case for the cassette. The storage case comprises locking members which are engageable in the holes in the reel hubs to inhibit rotation of the reel hubs. Such a solution cannot be adopted for cassettes of the type defined in the opening paragraph, the openings being covered by the slide cover when the cassette is outside a drive apparatus. However, the solution which has been adopted is comparatively intricate and requires the use of a separate moving part, i.e. the blocking member which is movable over the inner surface of the imperforate main wall. The blocking member requires a certain mounting height in the interior of the cassette, which results in a greater height of the cassette.